Heat reservoir impregnated with latent heat storage material with excellent thermostability

ABSTRACT

This invention provides a heat reservoir exhibiting improved thermostability at abnormally high temperatures. The heat reservoir  1  of the invention comprises: a plate-shaped porous substrate  10  having 2 main surfaces  11  and  12;  a heat storage material composition impregnating into the porous substrate  10;  and a coat layer  20  covering at least one of the 2 main surfaces  11  and  12  of the porous substrate  10,  wherein the heat storage material composition comprises a latent heat storage material and a thermoplastic elastomer and the coat layer  20  is thermostable and radiant heat reflective.

TECHNICAL FIELD

The present invention relates to a heat reservoir that can be used forvarious applications, such as building materials.

BACKGROUND ART

As typified by “smart houses,” concepts of “energy saving,” “energycreation,” and “energy storage” are keys to recent houses, andconstruction of comfortable houses that do not discharge carbon dioxideis intended. Meanwhile, there is a concept of “passive house,” and houseconstruction that has achieved high degrees of energy saving andcomfortability by providing a house with high level heat insulationefficiency has drawn attention. Every house is required to have achievedan improvement in heat insulation efficiency and properties dealing withthe thermal environment. Accordingly, research and developmentconcerning building materials capable of heat storage with the aid offloors and walls of a house, thereby achieving the energy-saving andcomfortable living environment, have been actively conducted.

For example, proposals and attempts of storing the natural energy suchas solar light, the thermal energy generated by an air-conditioningequipment, or the thermal energy generated in daily lives in latent heatstorage materials, and minimizing the changes in room temperaturethrough endothermic and/or exothermic reactions in accordance withchanges in external temperature have been made.

Documents such as Patent Documents 1 to 6 disclose techniques ofimparting building materials with heat storability by combining a latentheat storage material and a building material. Patent Documents 1 to 4each disclose a technique of impregnating porous wood molds with latentheat storage materials. Patent Document 5 discloses a heat reservoircomprising a porous material such as a plaster board which isimpregnated with a melt mixture of an ethylene-α-olefin copolymer at agiven density and a latent heat reservoir. Patent Document 6 discloses aheat storage board comprising a main body of the heat storage boardcomposed of an ethylene-based resin as a substrate, which is impregnatedwith a latent heat storage material, and a sheet sealing the entiresurface of the latent storage board.

A latent heat storage material uses a latent heat required for a phasetransition between the solid phase and the liquid phase. Accordingly,liquid exudation can be problematic. According to the techniquesdisclosed in Patent Documents 1 to 5, porous substrate matrix isimpregnated with latent heat storage materials, so as to prevent theliquid from exuding. According to the technique disclosed in PatentDocument 6, liquid exudation is prevented via sealing of the surface.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP Patent Publication (Kokai) No. 2014-180812 A-   Patent Document 2: JP Patent Publication (Kokai) No. 2014-180811 A-   Patent Document 3: JP Patent Publication (Kokai) No. 2014-140981 A-   Patent Document 4: JP Patent Publication (Kokai) No. 2014-140980 A-   Patent Document 5: JP Patent Publication (Kokai) No. 1-105-1281 A-   Patent Document 6: JP Patent Publication (Kokai) No. H06-34187 A

SUMMARY OF THE INVENTION Objects to be Attained by the Invention

Conventional heat reservoirs such as those disclosed in Patent Documents1 to 6 are aimed at suppression of exudation of latent heat storagematerials within a normal temperature range, and thermostability atabnormally high temperatures caused by fire and other reasons was nottaken into consideration.

For example, the heat reservoirs disclosed in Patent Documents 1 to 5may suffer from exudation of heat storage material compositions fromporous substrates at abnormally high temperatures. In the case of theheat reservoir disclosed in Patent Document 6, the substrate may exude.At abnormally high temperatures, disadvantageously, the exudedcomponents may catch fire.

In the past, there had been no heat reservoir having thermostability atabnormally high temperatures. Accordingly, it is an object of thepresent invention to provide a heat reservoir with improvedthermostability at abnormally high temperatures.

Means for Attaining the Objects

The present inventors found that thermostability of a heat reservoircomprising a plate-shaped porous substrate impregnated with a heatstorage material composition at abnormally high temperatures could beimproved by using a latent heat storage material supplemented with athermoplastic elastomer as a heat storage material composition andcovering at least one main surface of the plate-shaped porous substratewith a thermostable and radiant heat reflective layer. This has led tothe completion of the present invention.

Specifically, the heat reservoir according to the present inventioncomprises a plate-shaped porous substrate having 2 main surfaces, a heatstorage material composition impregnating into the porous substrate, anda coat layer covering at least one of the 2 main surfaces of the poroussubstrate, wherein the heat storage material composition comprises alatent heat storage material and a thermoplastic elastomer and the coatlayer is thermostable and radiant heat reflective.

According to the present invention, a porous substrate is impregnatedwith a heat storage material composition comprising a latent heatstorage material and a thermoplastic elastomer, so that exudation of aheat storage material composition from a porous substrate when heatedcan be suppressed more efficiently, compared with the case where aporous substrate is impregnated with a latent heat storage materialalone or the case where a porous substrate is impregnated with a heatstorage material composition comprising a high-melting-point componentother than a thermoplastic elastomer in combination with a latent heatstorage material. In addition, a porous substrate is impregnated with aheat storage material composition, and nails can thus be fixed at anyposition at the time of construction.

In addition, a porous substrate is provided with a thermostable coatlayer that is capable of reflecting the radiant heat. When the heatreservoir according to the present invention is provided in a mannersuch that the coat layer is exposed to the heat source, accordingly, atemperature rise occurring in the heat storage material compositionimpregnating into the porous substrate can be suppressed, exudation ofthe heat storage material composition can be suppressed, and the exudedheat storage material composition can be suppressed from burning. It ispreferable that the entire area of at least one main surface of theporous substrate be covered with a coat layer. As long as theaforementioned effects can be exerted, however, it may be acceptablethat a part of the at least one main surface of the porous substrate isnot covered with a coat layer. In such a case, such surface is coveredin an area of preferably 70% or more, more preferably 80% or more, stillmore preferably 90% or more, further preferably 95% or more, andfurthermore preferably 98% or more of the entire area.

According to a preferable embodiment of the present invention, thethermoplastic elastomer used for the heat reservoir is either anolefin-based thermoplastic elastomer or a styrene-based thermoplasticelastomer. With the use of such thermoplastic elastomer, exudation of aheat storage material composition from the porous substrate can beeffectively suppressed.

According to another preferable embodiment of the present invention,both of the 2 main surfaces of the porous substrate of the heatreservoir are covered with the coat layers, which are gas-impermeablelayers. Since the top surface and the back surface of the poroussubstrate are covered with gas-impermeable coat layers according to thisembodiment, a heat storage material composition can be prevented frombecoming volatile at high temperatures. Even if a volatile gas isgenerated, in addition, leaking of the volatile gas to the outside canbe mostly suppressed. By impregnating the porous substrate with a heatstorage material composition, elution of a heat storage materialcomposition in a lateral direction is confirmed to be low, compared withthe case in the absence of a porous substrate, as a result of theexperiment. When both surfaces are covered with coat layers as with thecase of the present embodiment, in addition, the substrate can beprovided without distinguishing the top surface from the bottom surface,and it can be thus handled easily. While it is preferable that theentire areas of both main surfaces of the porous substrate be coveredwith coat layers, it is acceptable that a part thereof is not covered,as long as the aforementioned effects can be exerted. In such a case,such surface is covered in an area of preferably 70% or more, morepreferably 80% or more, still more preferably 90% or more, furtherpreferably 95% or more, and furthermore preferably 98% or more of theentire area.

According to another preferable embodiment of the present invention,more preferably, a surface that connects the two main surfaces of theporous substrate of the heat reservoir according to the presentinvention is covered with the coat layer. According to this embodiment,side edge surfaces of the porous substrate are covered with thegas-impermeable coat layers, as well as the main surfaces. Accordingly,the melted heat storage material composition and the volatile gas can beprevented from exuding and leaking, respectively, more efficiently.While it is preferable that the entire area of the surface that connectsthe both main surfaces of the porous substrate be covered with a coatlayer, it is acceptable that a part thereof is not covered with the coatlayer, as long as the aforementioned effects can be exerted. In such acase, the surface that connects the both main surfaces of the poroussubstrate is covered with a coat layer in an area of preferably 70% ormore, more preferably 80% or more, still more preferably 90% or more,further preferably 95% or more, and furthermore preferably 98% or moreof the entire area.

According to another preferable embodiment of the present invention, thecoat layer of the heat reservoir is a metal layer. According to thisembodiment, thermostability and radiant heat reflective capacity ofinterest can be realized in a cost-effective manner.

The porous substrate impregnated with the heat storage materialcomposition of the heat reservoir according to the present invention canbe obtained by a method comprising a step of impregnation comprisingimpregnating the porous substrate with the liquefied heat storagematerial composition.

Effects of the Invention

The present invention may provide a heat reservoir having improvedthermostability at abnormally high temperatures that may be caused byfire or other reasons.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the correlation between the heating duration and the totalheat value in the heating test in Test 1.

FIG. 2 shows the correlation between the heating duration and theheating rate in the heating test in Test 1.

FIG. 3 shows a photograph of the product of the present invention (withthe side edge surface being covered) after the heating test in Test 1.

FIG. 4 shows a photograph of the product of the present invention(without the side edge surface being covered) after the heating test inTest 1.

FIG. 5 shows a photograph of a comparative product (without the sideedge surface being covered) after the heating test in Test 1.

FIG. 6 shows the results of Test 2.

FIG. 7 shows the results of evaluation of the influence of the molecularweight and the amount of a fixing agent added on impregnation thereofinto the board and exudation resistance thereof confirmed in ReferenceTest 1.

FIG. 8 schematically shows a cross section of the heat reservoir 1according to an embodiment of the present invention.

FIG. 9 schematically shows a cross section of the heat reservoir 1according to an embodiment of the present invention.

FIG. 10 schematically shows a cross section of the heat reservoir 1according to an embodiment of the present invention.

FIG. 11 schematically shows a cross section of an interior wallstructure using the heat reservoir 1 according to an embodiment of thepresent invention.

FIG. 12 schematically shows a cross section of an interior wallstructure using the heat reservoir 1 according to an embodiment of thepresent invention.

FIG. 13 schematically shows a cross section of an interior wallstructure using the heat reservoir 1 according to an embodiment of thepresent invention.

FIG. 14 schematically shows a cross section of an interior wallstructure using the heat reservoir 1 according to an embodiment of thepresent invention.

FIG. 15 schematically shows a cross section of an interior wallstructure using the heat reservoir 1 according to an embodiment of thepresent invention.

FIG. 16 schematically shows a cross section of an interior wallstructure using the heat reservoir 1 according to an embodiment of thepresent invention.

FIG. 17 schematically shows a cross section of an interior wallstructure using the heat reservoir 1 according to an embodiment of thepresent invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION Porous Substrate

Examples of porous substrates that can be used in the present inventioninclude a wooden molded article, an inorganic fiber substrate, and amineral substrate. Examples of wooden molded articles include asubstrate comprising wood fibers integrated therein and a substratecomprising wood chips integrated therein.

A substrate comprising wood fibers integrated therein has fine poresbetween the wood fibers. Thus, such substrate can be impregnated with alarge amount of a heat storage material composition. A substratecomprising wood fibers integrated therein can be obtained by integratingwood fibers with the aid of one or more adhesives selected from among anisocyanate adhesive, a phenol formaldehyde adhesive, a urea-formaldehydeadhesive, and a melamine formaldehyde adhesive, according to need, andforming the integrated wood fibers into a configuration of interest suchas a plate via pressure molding. Examples of wood fibers that can beused include those of tropical wood (e.g., lauan) and conifers (e.g.,pine and cedar). Molding may be performed via pressure heating. Thedensity of the substrate comprising wood fibers integrated therein ispreferably from 0.2 to 0.5 g/cm³, and more preferably 0.2 to 0.3 g/cm³.Typical examples of substrates comprising wood fibers integrated thereininclude boards made of wood fibers, such as a medium-density fiberboard(MDF) and an insulation board.

A substrate comprising wood chips integrated therein also has fine poresbetween the wood chips and inside the wood chips. Thus, such substratecan be impregnated with a large amount of a heat storage materialcomposition. A substrate comprising wood chips integrated therein can beobtained by integrating wood chips with the aid of one or more adhesivesselected from among an isocyanate adhesive, a phenol formaldehydeadhesive, a urea-formaldehyde adhesive, and a melamine formaldehydeadhesive, according to need, and forming the integrated wood chips intoa configuration of interest such as a plate via pressure molding.Examples of wood chips that can be used include those of tropocal wood(e.g., lauan) and conifers (e.g., pine and cedar). Molding may beperformed via pressure heating. The density of the substrate comprisingwood chips integrated therein is preferably from 0.2 to 0.6 g/cm³, andmore preferably 0.3 to 0.5 g/cm³. Typical examples of substratescomprising wood chips integrated therein include a particle board and anoriented strand board (OSB).

Examples of inorganic fiber substrates include those made of rock wool,glass wool, carbon fiber, and metal fibers, which may be formed intoplates or other configurations.

Examples of mineral substrates include a gypsum plaster board, a calciumsilicate board, and an autoclaved lightweight aerated concrete (ALC)board, which are prepared by forming minerals into a board (i.e.,mineral boards).

The porous substrate used in the present invention is a plate-shapedsubstrate comprising two main surfaces. The term “plate-shaped” refersto having a configuration showing two-dimensional extension in which thedimension in a direction perpendicular to the direction of the extension(i.e., a thickness direction) is relatively smaller than the dimensionin the other direction. A planar configuration is not particularlylimited, as long as the conditions described above are satisfied, and itis not necessary that dimensions in a thickness direction areconsistent. According to the present invention, the widest surface whenthe entire plate-shaped porous substrate is observed macroscopically,regardless of fine concaves and convexes on the microporous poresurfaces, is regarded as one main surface and the surface oppositetherefrom is regarded as the other main surface. The “two main surfaces”are composed of the one main surface and the other main surface, one ofsuch surfaces is generally referred to as a “top surface,” and the otheris referred to as a “back surface.” A person skilled in the art definesa side edge surface of the plate-shaped substrate as a “butt endsurface,” and surfaces other than the butt end surface are equivalent tothe main surfaces according to the present invention. It is notnecessary that each main surface be flat, and concaves and convexes maybe provided thereon.

A thickness of the plate-shaped porous substrate is not particularlylimited, and it is generally from 0.5 to 3.0 cm.

Heat Storage Material Composition

The heat storage material composition contained in the heat reservoiraccording to the present invention comprises at least a latent heatstorage material and a thermoplastic elastomer.

A typical latent heat storage material that can be used in the presentinvention undergoes a phase change from solid to liquid caused by, forexample, solar radiation heat provided by the sun light or heatgenerated by indoor air heating. From the viewpoint of the applicationas a residential heat storage building material, a phase changetemperature (i.e., a melting point) of a latent heat storage material ispreferably from 5° C. to 60° C. and more preferably from 15° C. to 35°C.

Representative examples of latent heat storage materials include:saturated aliphatic hydrocarbons, having typically 16 to 24 carbonatoms, such as n-paraffin or paraffin wax, which may comprisen-hexadecane, n-heptadecane, n-octadecane, n-nonadecane, or a mixture ofany thereof; mono- or polyunsaturated aliphatic hydrocarbons, havingtypically 16 to 24 carbon atoms, such as linear α-olefin, which maycomprise 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene,1-eicosene, or a mixture of any thereof; long chain fatty acids, whichmay comprise octanoic acid, capric acid, lauric acid, myristic acid, ora mixture of any thereof; esters of such fatty acids, and polyethercompounds, such as polyethylene glycol. In the case of a material thatmelts at 28° C., for example, n-octadecane may be selected, and in thecase of a material that melts at 18° C., n-hexadecane may be selected.Further, mixtures of a plurality of latent heat storage materials havingdifferent melting points as described above may be used.

In the present invention, a thermoplastic elastomer is added to suppressexudation of a latent heat storage material. A thermoplastic elastomerthat is added for such purpose may be referred to as a “fixing agent” inthis specification.

A thermoplastic elastomer is a polymeric material that is elastic aswith vulcanized rubber at room temperature and is softened and fluidizedat high temperatures. A thermoplastic elastomer is composed of a rubbercomponent having elasticity in its molecule (i.e., a soft segment) and amolecular constraint component for preventing plastic deformation (i.e.,a hard segment), and it has properties intermediate between rubber andplastics.

Examples of thermoplastic elastomers include one or more thermoplasticelastomers selected from the group consisting of polyamide thermoplasticelastomers (TPA), polyester thermoplastic elastomers (TPC), olefin-basedthermoplastic elastomers (TPO), styrene-based thermoplastic elastomer(TPS), urethane thermoplastic elastomers (TPU), and thermoplastic rubbervulcanizates (TPV) defined in JIS K6418, and other thermoplasticelastomers (TPZ). One or more thermoplastic elastomers selected fromamong olefin-based thermoplastic elastomers and styrene-basedthermoplastic elastomers are more preferable, one or more thermoplasticelastomers selected from among styrene-based thermoplastic elastomersare further preferable, and one or more thermoplastic elastomersselected from among hydrogenated styrene-based thermoplastic elastomersare the most preferable. A mixture of a plurality of different types ofthermoplastic elastomers may be used.

Examples of olefin-based thermoplastic elastomers includenon-crosslinked and partially crosslinked elastomers havingpseudo-crosslinked crystalline structures, and specific examples includea blend of polypropylene (PP) and ethylene propylene rubber (EPM)dispersed therein, a blend of PP and an ethylene-propylene-diene ternarycopolymer (EPDM) dispersed therein, and a blend of PP and EPDM dispersedand partially crosslinked therein.

A styrene-based thermoplastic elastomer may or may not be hydrogenated.

Examples of nonhydrogenated styrene-based thermoplastic elastomersinclude styrene-butadiene-styrene block copolymers (SBS) andstyrene-isoprene-styrene block copolymers (SIS).

Examples of hydrogenated styrene-based thermoplastic elastomers includestyrene-ethylene/butylene-styrene block copolymers (SEBS),styrene-ethylene/propylene block copolymers (SEP),styrene-ethylene/propylene-styrene block copolymers (SEPS),styrene-ethylene-ethylene/propylene-styrene block copolymers (SEEPS),and a mixture of two or more thereof. Styrene-ethylene/butylene-styreneblock copolymers (SEBS) and styrene-ethylene-ethylene/propylene-styreneblock copolymers (SEEPS) are particularly preferable.

Styrene content in a styrene-based thermoplastic elastomer is notparticularly limited, and styrene content is preferably 25% to 35%relative to the entire molecules by mass.

A ratio of a latent heat storage material to a thermoplastic elastomerin a heat storage material composition can be adequately selected.Relative to 100 parts by mass of the latent heat storage material, athermoplastic elastomer can be contained in an amount of preferably 3 to30 parts by mass, more preferably 5 to 25 parts by mass, furtherpreferably 5 to 20 parts by mass, still further preferably 5 to 17 partsby mass, and furthermore preferably 5 to 14 parts by mass. When athermoplastic elastomer is a styrene-based thermoplastic elastomer, suchrange is particularly suitable.

The weight average molecular weight of a thermoplastic elastomer can beadequately determined in accordance with a type of thermoplasticelastomer used, and it is preferably 50,000 to 250,000, and morepreferably 100,000 to 200,000. Such preferable range is particularlysuitable when a thermoplastic elastomer is a styrene-based thermoplasticelastomer.

In order to suppress exudation of a heat storage material compositioncontaining a latent heat storage material from a porous substrate andallow a heat storage material composition to impregnate into a poroussubstrate, a preferable weight average molecular weight of athermoplastic elastomer satisfies the condition (1) described below,provided that the weight average molecular weight is designated as X×10⁴and the amount of the thermoplastic elastomer relative to 100 parts bymass of the latent heat storage material in the heat storage materialcomposition is designated as Y parts by mass.

5≦X≦17;

5≦Y≦25;

if 5≦X<10, Y≧−2X+25; and

if 14<X≦17, Y≦−5X+90   Condition (1):

Condition (1) is concluded to be preferable on the basis of the resultsof evaluation of Reference Test 1 described below, which are summarizedin FIG. 7. In FIG. 7, the horizontal axis indicates the weight averagemolecular weight of a thermoplastic elastomer and the vertical axisindicates the amount thereof added. FIG. 7 shows the results ofcomprehensive evaluation of impregnation of the porous substrate withthe heat storage material composition and resistance to exudation fromthe substrate at three different scales, and there were no resultsevaluated as “poor”. Evaluation scales are as described in detail inReference Test 1. In FIG. 7, straight lines including line segments A toK are each represented by the following formulae.

-   Straight line including line segment A: X=5-   Straight line including line segment B: Y=−2X+25-   Straight line including line segment C: Y=5-   Straight line including line segment D: Y=−5X+90-   Straight line including line segment E: X=14-   Straight line including line segment F: Y=25-   Straight line including line segment G: Y=−2X+30-   Straight line including line segment H: Y=−(5/7)X+(120/7)-   Straight line including line segment I: Y=−(10/3)X+(185/3)-   Straight line including line segment J: Y=−1.25X+32.5-   Straight line including line segment K: Y=−X+30

Hereafter, the expressions “a straight line including line segment A” to“a straight line including line segment K” are merely referred to as“straight line A” to “straight line K,” respectively.

The range of (X and Y) satisfying the condition (1) above is equivalentto a region surrounded by straight lines A to F in FIG. 7.

In the present invention, in addition, a heat storage materialcomposition in which X and Y satisfy the condition (2) below ispreferably used.

if 5≦X<10, Y≧−2X+30 and Y≦−X+30;

if 10≦X<14, Y≧−(5/7)X+(120/7) and Y≦−1.25X+32.5; and

if 14≦X≦17, Y≧−(5/7)X+(120/7) and Y≦−(10/3)X+(185/3)   Condition (2):

The range of (X and Y) satisfying the condition (2) is equivalent to theregion surrounded by straight lines A, G, H, I, J, and K in FIG. 7. Onthe basis of the results of Reference Test 1 (FIG. 7), it can be saidthat, when the condition (2) is satisfied, exudation of the heat storagematerial composition from the porous substrate is less likely to occur,and the porous substrate can be impregnated with the heat storagematerial composition.

When the condition (1) or (2) is satisfied, in addition, the weightaverage molecular weight of the thermoplastic elastomer is preferably60,000 or greater (X≧6), more preferably 75,000 or greater (X≧7.5),further preferably 85,000 or greater (X≧8.5), and most preferably 90,000or greater (X≧9). The weight average molecular weight of thethermoplastic elastomer is preferably 160,000 or smaller (X≦16), morepreferably 150,000 or smaller (X≦15), and most preferably 140,000 orsmaller (X≦14). When the weight average molecular weight of thethermoplastic elastomer is within such range, it is highly likely thatexudation of the heat storage material composition from the poroussubstrate is suppressed, and the porous substrate is easily impregnatedwith the heat storage material composition because of a sufficiently lowviscosity level at the time of melting.

The weight average molecular weight is measured via gel permeationchromatography (GPC), and it is determined as a standard polystyreneequivalent molecular weight.

The amount of the thermoplastic elastomer is preferably 25 parts by massor less (Y≦25), more preferably 20 parts by mass or less (Y≦20), andfurther preferably 17.5 parts by mass or less (Y≦17.5), relative to 100parts by mass of the latent heat storage material. According to apreferable embodiment, the heat storage material composition comprisesthe thermoplastic elastomer in an amount of preferably 6 parts by massor more (Y≧6), and more preferably 7.5 parts by mass or more (Y≧7.5),relative to 100 parts by mass of the latent heat storage material. Whenthe amount of the thermoplastic elastomer added (Y) is within theaforementioned range, it is highly likely that exudation of the heatstorage material composition from the porous substrate is suppressed andthe porous substrate is easily impregnated with the heat storagematerial composition due to a sufficiently low viscosity level at thetime of melting.

The conditions (1) and (2) and further preferable conditions describedabove are particularly preferable when a hydrogenated styrene-basedelastomer is used as a thermoplastic elastomer.

The heat storage material composition is preferably a composition thatmelts to form a liquid having a viscosity of preferably 1,000 mPa·s orless, more preferably 500 mPa·s or less, further preferably 150 mPa·s orless, and most preferably 100 mPa·s or less, which is measured with theuse of a B-type viscometer. When the viscosity is within such range, theporous substrate can be easily impregnated with the heat storagematerial composition.

The viscosity was measured with the use of a Brookfield rotationalviscometer (a B-type viscometer) as defined in JTS Z8803-2011 and HSK7117-1. Measurement was carried out with the use of a B-type viscometermanufactured by Toki Sangyo Co., Ltd. (ABS-100) with a rotor size of No.1 at the rotation speed of 6 to 60 rpm.

Coat Layer

According to the present invention, a coat layer is thermostable andradiant heat reflective. The term “thermostable” refers to having aproperty such that a configuration can be maintained after it is exposedto a temperature of 200° C. to 600° C. in the air for 10 to 60 minutes.

The radiant heat is an electromagnetic wave in a wavelength regionincluding the infrared radiation (including the far infrared radiation)and the visible radiation, and heat is generated when a material absorbsthe radiant heat. Being radiant heat reflective means having an abilityto reflect the radiant heat. Because of such properties, specifically,the infrared radiation at the wavelength of 0.3 to 100 μm can bereflected by 80% or more.

In the present invention, the coat layer is more preferably agas-impermeable layer. The gas-impermeable layer may not only be a layerthat can prevent gas from permeating therethrough at all, or but also bea layer that can substantially prevent gas from permeating therethrough.At 30° C. to 120° C. or higher temperatures, a latent heat storagematerial constituting the heat storage material composition can beheated and gasified. The coat layer of the present invention preferablyhas gas impermeability to the extent that it is capable of blocking thegasified component of the heat storage material composition to permeatewithin the temperature range described above.

The coat layer of the present invention is preferably a metal layer. Itis preferable that a metal layer be mainly composed of at least onemetal selected from the group consisting of aluminum, copper, and iron.In the present invention, a metal layer may consist of metal throughoutthe area in a thickness direction. Alternatively, a metal layer maycomprise a metal layer integrated with a resin layer (or resin layers),such as polyethylene terephthalate, polypropylene, polyethylene, ornylon on either or both surface(s) thereof. A metal layer may be alaminate of a plurality of metal layers. The thickness of a metal layeris not particularly limited, and it is preferably 1 μm to 1 mm, and morepreferably 20 μm to 1 mm. The aforementioned thickness range ispreferable for a metal layer alone. When a metal layer is integratedwith the resin layer, the thickness of the metal layer component ispreferably within the range described above.

The most preferable metal layer is a thin metal film, and its thicknessis preferably 5 to 200 μm, and more preferably 20 to 200 μm. A thinmetal film may also be a laminate of a metal component and the resinlayer component. The aforementioned thickness range is preferable for ametal layer alone. When a metal layer is integrated with the resinlayer, the thickness of the metal layer component is preferably withinthe range described above. Since a thin metal film can be easily cut,processing of the heat reservoir of the present invention, such ascutting thereof into sizes of interest, can be easily performed. Inaddition, a thin metal film is preferable in terms of cost efficiencyand light weight.

The metal layer may be formed by allowing a metal sheet prepared inadvance to adhere to the surface of the porous substrate or forming athin metal film on the surface of the porous substrate via vapordeposition or other means. The metal sheet may be prepared via vapordeposition of a metal onto a sheet of the resin, or a sheet of the resinmay be laminated onto a metal sheet. A metal sheet that is commerciallyavailable in the form of a metal foil such as an aluminum foil can beused.

The coat layer and the porous substrate can be adhered to each otherthrough an adhesive layer provided therebetween, according to need.

Structure of Heat Reservoir

Examples of structures of the heat reservoir according to the presentinvention are shown in FIGS. 8 to 10. It should be noted that the scopeof the present invention is not limited to the embodiments shown in thefigures. Figures subsequent to FIG. 8 each schematically show a crosssection obtained by cutting a plate in the through thickness direction.In the figures, dimensions, such as a thickness and a width, of thelayers are exaggerated for illustrative purposes, and actual dimensionsare not reflected.

The heat reservoir 1 according to the present invention shown in FIG. 8comprises: a plate-shaped porous substrate 10 impregnated with a heatstorage material composition; and a coat layer 20 that covers a mainsurface 11 of two main surfaces 11 and 12 of the porous substrate 10.According to an embodiment shown in FIG. 8, the other main surface 12 ofthe porous substrate 10 and a surface 13 (i.e., a butt end surface) thatconnects the two main surfaces 11 and 12 are not covered with the coatlayer 20. The coat layer 20 is radiant heat reflective and thermostable.When the heat reservoir 1 is provided in such a manner that the coatlayer 20 faces a heat source, accordingly, a temperature rise occurringin the heat storage material composition that had impregnated into theporous substrate 10 can be suppressed. That is, the heat reservoir 1 hasthermostability.

In the heat reservoir 1 shown in FIG. 8, an additional layer may beadequately present between the porous substrate 10 and the coat layer 20(not shown). The same applies to embodiments shown in other figures. Anexample of such an additional layer is an adhesive layer that bonds theporous substrate 10 to the coat layer 20.

According to an embodiment of the heat reservoir 1 shown in FIG. 9, boththe main surfaces 11 and 12 of the porous substrate 10 are covered withthe coat layers 20. In such a case, the heat reservoir 1 can be providedwithout distinguishing the top surface from the bottom surface. Inaddition, both the two main surfaces 11 and 12 are covered with the coatlayers 20. Thus, exudation of the heat storage material composition andleaking of the gasified heat storage material composition can be moreeffectively suppressed. According to this embodiment, the coat layer 20is preferably gas-impermeable.

An embodiment of the heat reservoir 1 shown in FIG. 10 is furtherimproved from the embodiment shown in FIG. 9. According to suchembodiment, a surface 13 (i.e., a butt end surface) that connects thetwo main surfaces 11 and 12 is also covered with the coat layer 20, aswell as the two main surfaces 11 and 12 of the porous substrate 10.According to this embodiment, the butt end surface 13 is also coveredwith the coat layer 20, as well as the two main surfaces 11 and 12 ofthe porous substrate 10. Accordingly, exudation of the melted heatstorage material composition and leaking of volatile gas can be moreeffectively suppressed. It is preferable that the entire surface of theporous substrate 10 be covered with the coat layer 20.

Method for Producing Heat Reservoir

The heat reservoir according to the present invention can be produced bya method comprising a step of impregnation in which a heat storagematerial composition liquefied by melting is allowed to penetrate intothe porous substrate and a subsequent step of coating in which at leastone main surface of the porous substrate impregnated with the heatstorage material composition is covered with a coat layer.

A melted product of the heat storage material composition can beprepared by mixing the latent heat storage material and thethermoplastic elastomer and heating the mixture to a temperature atwhich both components become liquefied. Such components are liquefiedpreferably at 80° C. to 140° C. and more preferably at 100° C. to 130°C.

According to an embodiment of the step of impregnation, the poroussubstrate is soaked in the liquefied heat storage material compositionmelted in a tank, so as to allow the heat storage material compositionto penetrate into the porous substrate (i.e., the inside of the pores ofthe substrate). According to another embodiment of the step ofimpregnation, the liquefied heat storage material composition is pouredor applied onto the porous substrate surface, so as to allow the heatstorage material composition to penetrate into the porous substrate(i.e., the inside of the pores of the substrate).

The porous substrate impregnated with the heat storage materialcomposition is obtained by cooling the substrate after the step ofimpregnation, so as to solidify the heat storage material composition(the step of solidification). The cooling may be performed via anymeans. Prior to the step of solidification, according to need, theporous substrate after the step of impregnation is allowed to standupright, so as to perform liquid draining. Through this liquid draining,part of the heat storage material composition deposited on the poroussubstrate surface or the heat storage material composition impregnatinginto the porous substrate may be removed.

The step of coating may be performed without particular limitation. Acoat layer may be formed on the main surface of the porous substrateimpregnated with the heat storage material composition. Alternatively, asheet constituting the coat layer may be prepared in advance and theresulting sheet may be allowed to adhere to the main surface.

Application Examples of the Heat Reservoir

The heat reservoir 1 according to the present invention can be used in awide variety of situations where heat storability is desired.Representative examples of applications as wall materials, floormaterials, ceiling materials, and other materials are described below.In the description provided below, elements having similar functions andstructures are indicated with the same numeral references, anddescriptions thereof are omitted.

(FIG. 11)

FIG. 11 shows an embodiment of an interior wall structure comprising theheat reservoir 1 and, on the indoor side thereof, a laminate of adecorative substrate 111 and a decorative material 112.

The decorative substrate 111 is not particularly limited, provided thatit is a plate-shaped material used as a building material. Examplesthereof that can be used include: inorganic plate materials, such as agypsum plaster board and a calcium silicate board; woody platematerials, such as a plywood and MDF; and metal plate materials, such asa copper board and an aluminum board.

The decorative material 112 is formed by subjecting the decorativesubstrate 111 to processing, such as printing, coating, or lamination.Examples thereof include a decorative material which is formed bysubjecting the decorative substrate 111 to decorative printing and thencoating with urethane or polyester, a decorative material which isformed by laminating a paper, a vinyl chloride sheet, and an olefinsheet having decorative printing, and a decorative material which isformed by applying various types of finishing materials, such as a cloth(e.g., paper, vinyl, and fabric), a plaster, a wood, a cork, a tile, anda stone, on the surface of the decorative substrate 111.

As a building material made of the decorative substrate 111 and thedecorative material 112, a board material that has been decorated inadvance, such as a melamine decorative laminate plate, can be used.

(FIG. 12)

FIG. 12 shows an embodiment of an interior wall structure comprising theheat reservoir 1, on the indoor side thereof, a laminate of a decorativesubstrate 111 and a decorative material 112 as shown in FIG. 11, and aheat insulator 121 laminated on the outdoor side of the heat reservoir1.

Examples of the heat insulator 121 that can be used include polystyrenefoam, polyethylene foam, phenolic foam, glass wool, rock wool, urethanefoam, a wood fiber board, an insulation board, and a sheep wool board. Aplurality of types of heat insulators 121 may be used in adequatecombination.

By providing the heat insulator 121 on the outdoor side of the heatreservoir 1, at the time of heat storage or discharge, the heat can beprevented from leaking from the heat reservoir 1 to the outside.

(FIG. 13)

FIG. 13 shows another embodiment of the interior wall structure shown inFIG. 12, which further comprises an aluminum heat shield film 131provided on the surface of the outdoor side of the heat insulator 121.

The aluminum heat shield film 131 may be prepared by laminating analuminum sheet (an aluminum foil) on the surface of the heat insulator121, or it may be formed as an aluminum layer on the surface of the heatinsulator 121 via vapor deposition.

Because of the heat shield effects, the aluminum heat shield film 131can reflect and suppress the radiant heat entering from outdoor toindoor.

(FIG. 14) (FIG. 15)

FIG. 14 shows an embodiment of an interior wall structure comprising theheat reservoir 1, on the indoor side thereof, a heater or hot/cold waterpanel 141, the decorative substrate 111, and the decorative material 112provided in that order, and the heat insulator 121 on the outdoor sideof the heat reservoir 1.

FIG. 15 shows an embodiment of an interior wall structure comprising theheat reservoir 1, on the indoor side thereof, the decorative substrate111 and the decorative material 112 provided in that order, and theheater or hot/cold water panel 141 and the heat insulator 121 on theoutdoor side of the heat reservoir 1.

Examples of the heater or hot/cold water panel 141 that can be usedinclude an electric heater panel, a sheet heating element, hot and coldwater pipes, and a hot and cold water unit.

In the structure as shown in FIG. 14 or 15, a heating or cooling mediummay be provided adjacent to the heat reservoir 1 on the indoor oroutdoor side thereof, so as to forcibly store a heat or a cold source.Such structure can be effectively used for midnight power service. Suchstructure can be used for heating and cooling on the floor, the wall,and the ceiling.

(FIG. 16) (FIG. 17)

FIG. 16 shows another embodiment of the interior wall structure shown inFIG. 14 comprising an aluminum heat shield film 131 laminated on theoutdoor side of the heat insulator 121.

FIG. 17 shows another embodiment of the interior wall structure shown inFIG. 15 comprising an aluminum heat shield film 131 laminated on theoutdoor side of the heat insulator 121.

Because of the heat shield effects, the aluminum heat shield film 131can reflect and suppress the radiant heat entering from outdoor toindoor.

EXAMPLES

In the following tests, “part” is “by mass.”

[Test 1: Comparison of the Heat Reservoir of the Present Invention and aCommercially Available Heat Reservoir] 1. Objective

This test is intended to inspect the incombustibility of the heatreservoir according to the present invention, which is prepared bycovering a wood fiber board impregnated with a heat storage materialcomposition as a prototype with an aluminum foil.

2. Test Subject (Invention Product)

An insulation board (density: 0.27 g/cm³; thickness: 10 mm) was used asa plate-shaped porous substrate. An insulation board is prepared in theform of a plate from a wood fiber as a starting material via molding,and its density is less than 0.35 g/cm³.

As a latent heat storage material, a olefin (melting point: 32° C.) wasused. This a olefin is composed of 5% by mass or less of C₁₈, 40 to 60%by mass of C₂₀, 25 to 50% by mass of C₂₂, 18% by mass or less of C₂₄,and 1% by mass or less of C₂₆ α olefins.

As a fixing agent, a hydrogenated styrene-based thermoplastic elastomer(SEEPS) was used. The weight average molecular weight of the fixingagent was 100,000.

As a coat material constituting a coat layer, an aluminum foil (aluminumlayer thickness: 50 μm, soft) was used.

As an adhesive that bonds the substrate to the coat material, anacrylic-styrene copolymer emulsion was used.

The test subject of the heat reservoir according to the presentinvention was prepared with the use of the materials described above inaccordance with the following procedure (hereafter, it is referred to as“the invention product,” according to need).

The latent heat storage material (100 parts by mass) was melt-mixed with15 parts by mass of the fixing agent in a kneader at 120° C., and a heatstorage material composition comprising the fixing agent mixed with thelatent heat storage material was prepared.

The heat storage material composition was heat-melted at 120° C. in avat, the substrate (200×200 mm) was soaked in the molten composition,and the substrate was impregnated with the heat storage materialcomposition. The duration of soaking was 10 minutes.

The substrate was removed from the vat 10 minutes after the initiationof soaking, and the coat material was allowed to adhere to the topsurface and the back surface of the substrate over the entire area withthe aid of the adhesive to form coat layers. Thus, the invention productwas prepared.

(Comparative Product)

As a comparative heat reservoir, a commercially available product wasused. Specifically, the commercially available product is a heat storagepanel, which is a plate-shaped substrate with a thickness of 5.3 mmcomposed of a gel-type heat storage material composition comprisingparaffin with a melting point of 22° C. and an ethylene-base polymer ata ratio of 60:40 by mass, with the top surface and the back surfacethereof being covered with an aluminum foil (aluminum layer thickness:100 μm, hard).

3. Test Method 3.1. Method of Evaluation

The heating test defined in Attachment A of JIS A 5404 in accordancewith the ISO cone calorimeter method was performed.

This test is carried out with the use of an apparatus that heats a10-cm-square test subject (10×10 cm) with the use of a cone-type heaterand measures the oxygen concentration in the generated gas. The testsubject is heated at 50 kW/m² (heater temperature: about 760° C.) tocatch fire from electric sparks. On the basis of the oxygenconcentration reduced as a result of combustion, the heat value and theheating rate are calculated. The test method is described in detail inAttachment A of JIS A 5404. In principle, this test is carried out withthe back surface and the side surfaces of the test subject being coveredwith aluminum foils.

The criteria for evaluation in this test are as described below (inaccordance with Attachment A of JIS A 5404).

The materials satisfying all the conditions (1) to (3) within the givenperiod of time (i.e., 20 minutes) are evaluated as “incombustiblematerials,” the materials satisfying all the conditions (1) to (3)within the given period of time (i.e., 10 minutes) are evaluated as“semi-incombustible materials,” and the materials satisfying all theconditions (1) to (3) within the given period of time (i.e., 5 minutes)are evaluated as “flame-retardant materials.”

(1) The total heat value within the given period of time after theinitiation of heating is 8 MJ/m₂ or less.

(2) The maximal heating rate within the given period of time after theinitiation of heating is continuously not more than 200 kW/m² for atleast 10 seconds.

(3) There are no cracks or holes that reach the back surface, which areharmful from the viewpoint of fire prevention, up to the given period oftime elapsed after the initiation of heating.

3.2 Treatment Conditions for Test Subject

For both the invention product and the comparative product, the testsubject with the side surface thereof being covered with an aluminumtape (hereafter referred to as a “side-surface-covered”) and the testsubject with the side surface thereof being uncovered (hereafterreferred to as a “side-surface-uncovered”) were prepared.

(Side-Surface-Covered)

The side surfaces of the 10-cm² test subject were covered with analuminum tape (there was no aluminum foil covering at the time of thetest).

(Side-Surface-Uncovered)

The side surfaces of the 10-cm² test subject were not covered with analuminum tape.

4. Evaluation Results 4.1. List of Results

The test results are shown in FIG. 1 and FIG. 2. FIG. 1 shows thecorrelation between the heating duration and the total heat value. FIG.2 shows the correlation between the heating duration and the heatingrate.

The results of evaluation concerning incombustibility based on the testresults are as shown below.

TABLE 1 Invention Invention Comparative Comparative product productproduct product (side- (side- (side- (side- surface- surface- surface-surface- covered) uncovered) covered) uncovered) Total heat value ⊚(0.21) ⊚ (2.34) ⊚ (0.12) ◯ (9.03) (MJ/m²) Maximum ⊚ ⊚ ⊚ ◯ heating rateMaximum 2.85 13.02 4.01 229.31 rate (kW/m²) Length of time 0 0 0 8.5during which the rate exceeds 200 kW/m² (sec) Through crack ⊚ ⊚ ⊚ ◯ * ⊚:incombustible; ◯: Semi-Incombustible; Δ: flame-retardant

When the side surfaces of the test subject were covered with aluminumtapes, neither the invention product nor the comparative product caughtfire for 20 minutes after the initiation of heating.

When the side surfaces of the test subject were not covered with tapes,the invention product caught fire at the edge about 10 minutes after theinitiation of heating. Thereafter, the test subject repeatedly caughtfire and quenched the fire.

When the side surfaces of the test subject were not covered with tapes,the comparative product caught fire at the edge about 10 minutes afterthe initiation of heating, the heat storage material composition wasthen exuded at the edge from the inside, and combustion spread rapidly.

4.2.Conditions after Heating Test

FIGS. 3 to 5 each show a photograph showing the condition of the testsubject after the heating test.

FIG. 3 shows a photograph of the invention product(side-surface-covered) after the test. When the side surfaces of thetest subjects were covered with aluminum tapes, heat storage materialsand the like in the test subjects of the invention product and of thecomparative product were volatilized via heating, and aluminum foilscovering the surfaces became swollen.

FIG. 4 shows a photograph of the invention product(side-surface-uncovered) after the test. The test subject of theinvention product (side-surface-uncovered) caught fire at the edge, aburned mark remained therein, but the fiber board inside thereof was notsubstantially burned.

FIG. 5 shows a photograph of the comparative product(side-surface-uncovered) after the test. When the side surfaces of thetest subject of the comparative product were not covered with aluminumtapes, the comparative product caught fire at the edge about 10 minutesafter the initiation of heating, the heat storage material compositionwas then exuded at the edge of the test subject from the inside, andcombustion spread rapidly.

5. Conclusion

As a result of the tests described above, the substrate could be madeincombustible by covering the main surface of a wood fiber boardimpregnated with the heat storage material composition with an aluminumfoil even if the heat storage material composition itself is highlylikely to catch fire.

The invention product comprises a wood fiber board impregnated with aheat storage material composition. Because of such structure, it wasconfirmed that the heat storage material composition would be lesslikely to flow out of the structure even if it was heated, andcombustion could be suppressed.

[Test 2: Confirmation of Heat-Shielding Properties of Aluminum Foil] 1.Objectives

Aluminum is known to be a material exerting high heat-shielding effectson the radiant heat. The panel impregnated with the heat storagematerial composition was made flame retardant as a result of coveringthereof with an aluminum foil as confirmed in Test 1. This is consideredto result from a high degree of heat-shielding properties of an aluminumfoil. By covering the panel impregnated with the heat storage materialcomposition with an aluminum foil, heat transfer to the inside of thepanel may change to a significant extent. Accordingly, the followingtest was intended to evaluate the influence of covering with an aluminumfoil.

2. Test Subject

As the test subject, the invention product covered with an aluminum foilon its top and back surfaces prepared in Test 1 was used.

As a comparative sample, an insulation board impregnated with the heatstorage material composition, which is the invention product without analuminum foil covering its top and back surfaces, was used.

3. Method of Evaluation

A container was provided in an environmental test chamber, the testsubject was introduced in the container and placed therein at 10° C. Andthen, the test subject was allowed to stand at 40° C. for 7 hours andthen at 10° C. for 7 hours. During the storage test, the surfacetemperature of the test subject was measured with the elapse of time.

4. Results

The results are shown in FIG. 6. It was confirmed that temperaturechange of the panel could be made moderate by covering the heatreservoir surface with an aluminum foil.

5. Conclusion

The heat storage material composition can moderate the temperaturechange rate. In addition, the temperature change rate could be madefurther moderate by covering the surface with aluminum foil.

In the tests detailed below, the viscosity was measured by the methodinvolving the use of a Brookfield rotational viscometer (a B-typeviscometer) as defined in JIS Z8803-2011 and JIS K7117-1. Measurementwas carried out with the use of a B-type viscometer manufactured by TokiSangyo Co., Ltd. (ABS-100) with a rotor size of No. 1 at the rotationspeed of 6 to 60 rpm.

[Reference Test] 1. Reference Test 1

This test is intended to evaluate the impregnation performance of amixture of the latent heat storage material (paraffin) and a fixingagent when a woody board is impregnated with it, and exudationresistance (i.e., the retention ability) of the mixture.

1.1 Materials

As a woody board, an insulation board (density: 0.27 g/cm³; thickness:15 mm) was used. An insulation board was prepared in the form of a platefrom a wood fiber as a starting material via molding, and its densitywas less than 0.35 g/cm³.

As a latent heat storage material, n-paraffin comprising 18 carbon atoms(melting point: 28° C.) was used.

As a fixing agent, a hydrogenated styrene-based thermoplastic elastomerwas used. As a hydrogenated styrene-based thermoplastic elastomer, astyrene-ethylene/butylene-styrene block copolymer (SEBS) with the weightaverage molecular weight of 50,000, 100,000, 140,000, or 170,000 wasused.

1.2 Test Method

The latent heat storage material (paraffin) and the fixing agent wereadded at the ratio shown in Table 2, they were melt-mixed in a kneaderat 100° C. to 130° C., and mixtures of the fixing agent and the latentheat storage material (i.e., the heat storage material compositions)were prepared.

Each heat storage material composition was heat-melted at 100° C. to110° C. in a vat, the insulation board (200×200 mm) was soaked in themolten composition, and the insulation board was impregnated with theheat storage material composition. The duration of soaking was 10minutes.

(Evaluation 1) Influence of the Molecular Weight and the Amount of theFixing Agent Added on the Impregnation Performance

The insulation board was removed from the vat 10 minutes after theinitiation of soaking. The condition of impregnation of the insulationboard with the heat storage material composition was graded at a levelof “good”, “moderate,” and “poor”. In addition, the weight measuredbefore soaking was compared with that measured after soaking todetermine the impregnation rate.

(Evaluation of Impregnation Performance)

-   Good: Conditions of impregnation are satisfactory, liquid draining    of the heat storage material composition is satisfactory, and    substantially no coating of the heat storage material composition is    formed on the board surface.-   Moderate: A certain degree of impregnation is attained, liquid    draining of the heat storage material composition is not very good,    and a coating of the heat storage material composition is formed in    a small area on the board surface.-   Poor: Conditions of impregnation are poor, liquid draining of the    heat storage material composition is poor, and a coating of the heat    storage material composition is formed on the entire board surface.

Impregnation rate=(board weight after impregnation−board weight beforeimpregnation)/(board weight before impregnation)×100 (%)

In addition, the viscosity of the heat storage material composition at100° C. was measured with the use of a B-type viscometer.

(Evaluation 2) Influence of the Molecular Weight and the Amount of theFixing Agent Added on Resistance to Exudation of the Heat StorageMaterial Composition to the Outside from the Board

The board impregnated with the heat storage material composition wasallowed to stand in a dryer at 40° C. for 1 month. A decrease in theboard weight was determined before and after the 1 month so as tocalculate the rate of exudation of the heat storage material compositionfrom the board.

Exudation rate=(board weight before the 1 month−board weight after the 1month)/(board weight before the 1 month)×100 (%)

(Evaluation of Exudation Resistance)

-   Good: Exudation rate of 0%-   Moderate: Exudation rate greater than 0% and less than 1%-   Poor: Exudation rate of 1% or greater

(Comprehensive Evaluation)

The fixing agent was subjected to comprehensive evaluation in terms ofboth the impregnation performance of the heat storage materialcomposition into the board and the resistance to exudation of thecomposition from the board.

-   Good: Both impregnation performance and exudation resistance are    good.-   Moderate: Either impregnation performance or exudation resistance is    good and the other is moderate or both impregnation performance and    exudation resistance are moderate.-   Poor: Either or both impregnation performance and exudation    resistance is(are) poor.

1.3 Results

Table 2 and FIG. 7 show the results of evaluation.

FIG. 7 shows a graph plotting the results represented by “good”,“moderate,” and “poor” of the comprehensive evaluation. In FIG. 7, themolecular weight and the amount of the fixing agent added are preferablywithin the region surrounded by straight lines A, B, C, D, E, and F, andmore preferably within the region surrounded by straight lines A, G, H,I, J, and K. Formulae indicating the straight lines are as describedabove.

TABLE 2 Influence of the molecular weight and the amount of the fixingagent added on impregnation and exudation resistance of the boardViscosity of Molecular heat storage Impregnation weight of Amount ofcomposition performance 10-minutes Exudation Resistance fixing agentfixing agent at 100° C. Liquid impregnation rate after to exudationComprehensive (unit: 10000) added (parts) (mP · s) draining rate (%) 1month (%) from board evaluation 5 15 45 Good 161 0.2 Moderate Moderate20 100 Good 116 0 Good Good 25 180 Good 89 0 Good Good 10 5 10 Good 1880.4 Moderate Moderate 10 35 Good 133 0 Good Good 15 150 Good 110 0 GoodGood 20 320 Good 77 0 Good Good 25 550 Moderate 42 0 Good Moderate 14 520 Good 132 0.3 Moderate Moderate 10 50 Good 100 0 Good Good 15 210 Good91 0 Good Good 20 490 Moderate 43 0 Good Moderate 25 1000 Moderate 20 0Good Moderate 17 2 95 Good 106 0 Good Good

2. Reference Test 2

This test is intended to evaluate the impregnation performance of amixture of the latent heat storage material (a-olefin) and a fixingagent when a woody board is impregnated with the mixture.

2.1. Materials

As a woody board, an insulation board (density: 0.27 g/cm³ ; thickness:15 mm) was used.

An insulation board was prepared in the form of a plate from a woodfiber as a starting material via molding, and the density thereof wasless than 0.35 g/cm³.

As a latent heat storage material, α olefin (melting point: 32° C.) wasused. This α olefin is composed of 5% by mass or less of C₁₈, 40 to 60%by mass of C₂₀, 25 to 50% by mass of C₂₂, 18% by mass or less of C₂₄,and 1% by mass or less of C₂₆ α olefins.

As a fixing agent, a hydrogenated styrene-based thermoplastic elastomerwas used. As the hydrogenated styrene-based thermoplastic elastomer, astyrene-ethylene/butylene-styrene block copolymer (SEBS) with the weightaverage molecular weight of 100,000 or 170,000 was used.

2.2 Test Method (Evaluation) Influence of Melt Viscosity of a Mixture ofa Latent Heat Storage Material (a Olefin) and a Fixing Agent onImpregnation Performance

The latent heat storage material (α olefin) and the fixing agent wereadded at the ratio shown in Table 3, they were melt-mixed in a kneaderat 100° C. to 130° C., and mixtures of the fixing agent and the latentheat storage material (i.e., the heat storage material compositions)were prepared.

The heat storage material composition was heat-melted at 100° C. to 110°C. in a vat, the insulation board (200×200 mm) was soaked in the moltencomposition, and the insulation board was impregnated with the heatstorage material composition. The duration of soaking was 10 minutes.

The insulation board was removed from the vat 10 minutes after theinitiation of soaking, and the weight measured before soaking wascompared with that measured after soaking to determine the impregnationrate.

Impregnation rate=(board weight after impregnation−board weight beforeimpregnation)/(board weight before impregnation)×100 (%)

At the same time, the viscosity of the heat storage material compositionat 100° C. was measured with the use of a B-type viscometer.

2.3. Results

The results are shown in Table 3. When a olefin was used as the latentheat storage material, the heat-melted viscosity of the mixture of thelatent heat storage material and the fixing agent (i.e., the heatstorage material composition) and the impregnation performance thereofinto the insulation board were substantially equivalent to the resultsof Evaluation 1 of Reference Test 1 in which paraffin was used as thelatent heat storage material.

TABLE 3 Viscosity and impregnation rate of a mixture of a latent heatstorage material and a fixing agent (i.e., heat storage materialcomposition) Molecular Amount α-Olefin Paraffin weight of of fixingViscosity Impreg- Viscosity Impreg- fixing agent agent added of mixturenation of mixture nation (unit: 10000) (parts) mPa · s rate % mPa · srate % 10 5 12 182 10 188 10 10 40 128 35 133 10 15 146 106 150 110 17 5100 100 95 106

3. Reference Test 3

This test is intended to evaluate the performance of impregnation of thelatent heat storage material into an inorganic fiber board.

3.1. Materials

As substrates to be impregnated, an insulation hoard (IB) and a rockwool board (RB) were used.

An insulation board was a low-density wood fiber board (thickness: 12mm; density: 0.26 g/cm³).

A rock wool board was a low-density inorganic fiber board, which wasprepared by dissolving iron and steel slags at high temperature togenerate artificial mineral fibers, and forming the artificial mineralfibers into a board (thickness: 11 mm; density: 0.34 g/cm³).

As a latent heat storage material, α olefin (melting point: 32° C.) wasused. This a olefin is composed of 5% by mass or less of C₁₈, 40 to 60%by mass of C₂₀, 25 to 50% by mass of C₂₂, 18% by mass or less of C₂₄,and 1% by mass or less of C₂₆ α olefins.

As a fixing agent, a hydrogenated styrene-based thermoplastic elastomer(styrene-ethylene/butylene-styrene block copolymer (SEBS)) with theweight average molecular weight of 100,000 was used.

3.2 Test Method

The SEBS was added in an amount of 15 parts to 100 parts of the latentheat storage material, they were melt-mixed in a kneader at 100° C. to130° C., and a mixture of the fixing agent and the latent heat storagematerial (i.e., the heat storage material composition) was prepared.

The heat storage material composition was heat-melted at 100° C. to 110°C. in a vat, the insulation board (200×200 mm) was soaked in the moltencomposition, and the insulation board was impregnated with the mixture.The durations of soaking were 2, 5, 10, and 20 minutes.

(Evaluation 1) Evaluation of the Impregnation Performance of the HeatStorage Material Composition into the Board

The substrate was removed from the vat after the elapse of the givenperiod of soaking, and the weight measured before soaking was comparedwith that measured after soaking to determine the impregnation rate.

Impregnation rate=(board weight after impregnation−board weight beforeimpregnation)/(board weight before impregnation)×100 (%)

Impregnation amount=board density (kg/m³)×board thickness(m)×impregnation (%)/100 (kg/m²)

(Evaluation 2) Evaluation of Resistance to Exudation of the Heat StorageMaterial Composition to the Outside from the Board

The board impregnated with the heat storage material composition wasallowed to stand in a dryer at 40° C. for 1 month. A decrease in theboard weight was determined before and after the 1 month so as tocalculate the rate of exudation of the heat storage material compositionfrom the board.

Exudation rate=(board weight before the 1 month−board weight after the 1month)/(board weight before the 1 month)×100 (%)

5.3 Results

The results are shown in Table 4.

TABLE 4 Impregnation time, impregnation rate, impregnation amnount, andexudation rate of IB and RB Impreg- Impreg- Impreg- Substrate nationnation nation Exudation to be Density time rate amount rate impregnatedg/cm³ Minute % kg/m^(z) % IB 0.26 2 117 3.7 0 0.26 5 153 4.8 0 0.26 10203 6.3 0 0.27 20 197 6.4 0 RB 0.35 2 120 5.0 0 0.34 5 146 6.0 0 0.34 10155 6.3 0 0.34 20 147 6.0 0

RB showed an impregnation amount comparable to that of IB. Accordingly,it was confirmed that the heat storage material composition wouldsatisfactorily impregnate into inorganic fiber boards, as well as intoorganic fiber boards. While RB exhibited a lower impregnation rate thanIB, such difference was caused by different board densities.

The boards comprising RB and IB impregnated with the heat storagematerial composition, respectively, were allowed to stand in a dryer at40° C. for 1 month. As a result, the exudation rates of the heat storagematerial composition from such boards were found to be 0%.

4. Reference Test 4

This test is intended to find a fixing agent that is excellent inimmobilization of a latent heat storage material (paraffin) andexcellent in impregnation when beat melted.

4.1 Materials

As a latent heat storage material, n-paraffin comprising 18 carbon atoms(melting point: 28° C.) was used.

As a hydrogenated styrene-based thermoplastic elastomer, astyrene-ethylene/butylene-styrene block copolymer (SEBS) with the weightaverage molecular weight of 280,000 was used.

4.2 Test Method

A fixing agent (10 parts) was added to 100 parts of a latent heatstorage material, and the mixture was melt-mixed with heating at 100° C.to 1 30° C. As fixing agents, the agents shown in the table below wereused.

The mixture was melted at 100° C., and the viscosity was evaluated inthat state with the use of a B-type viscometer.

About 100 g of the melt mixture was introduced into a 200-cc cup, andthe mixture was cooled to solidify at 20° C.

4.3 Evaluation of Fixing Agent Performance Evaluation 1:

The cup containing the solidified mixture was placed in a dryer at 40°C., and the conditions of the mixture and the occurrence of exudation ofthe latent heat storage material were inspected 1 day later.

Evaluation 2:

Many holes each having a diameter of about 2 mm were opened at thebottom of the cup containing the solidified mixture, the cup was storedin a dryer at 40° C. for 3 days, and the amount of the exuding substancewas evaluated. In addition, whether or not the exuding substance was thelatent heat storage material or the mixture of the latent heat storagematerial and the fixing agent was evaluated. The amount of the exudingsubstance was determined in terms of a percentage of the mass of theexuding substance over the mass of the tested mixture.

4.4. Results of Evaluation 1

The results of Evaluation 1 (in terms of the status of compositions andevaluation of exudation when heated at 40° C.) are shown in Table 5.

When the hydrogenated styrene-based thermoplastic elastomer was used asa fixing agent, exudation was not observed when the latent heat storagematerial was liquefied (40° C.), and the mixture remained in a gelstate.

TABLE 5 Heat storage material/fixing agent mixture (heat storagematerial composition) Fixing agent Viscosity Material Exudation ofMelting Molecular when melted state when heat storage point weight at100° C. heated at material when Type (° C.) (unit: 10000) (mPa · s) 40°C.^(*1) heated at 40° C. Paraffin wax 69 — 5 X — Polyethylene wax 64 — 5X — Polyethylene wax 107 — 5 X — Low-density polyethylene 90 — 80 ◯Occurred Ethylene/vinyl acetate copolymer resin 89 — 30 ◯ OccurredHydrogenated styrene-based thermoplastic elastomer — 28 1,000 or more ◯Not occurred 12-Hydroxystearic acid 75 — 5 ◯ Occurred ^(*1)Materialstate when heated at 40° C.: ◯: gel: Δ: highly viscous liquid: X: liquid

4.5. Results of Evaluation 2

The results of Evaluation 2 (i.e., evaluation of the amount of elutionand the eluted substance when stored at 40° C.) are shown in Table 6.

In the case of the test groups involving the use of substances otherthan elastomers as fixing agents, only the latent heat storage materialwas liquefied when heated at 40° C., and it was eluted from the mixture.

When a hydrogenated styrene-based thermoplastic elastomer was used as afixing agent, it was found that elution occurring when heated at 40° C.could be suppressed.

TABLE 6 Heat storage material/fixing agent mixture (heat storagematerial composition) Fixing agent Viscosity Exudation rate when MeltingMolecular when melted heated at 40° C. point weight at 100° C. 1 daylater 3 days later Substance exuding Type (° C.) (unit: 10000) (mPa · s)(%) (%) when heated at 40° C. Low-density polyethylene 90 — 80 17.3 20.5Heat storage material Ethylene/vinyl acetate 89 — 30 33.5 38.4 Heatstorage material copolymer resin Hydrogenated styrene-based — 28 1,000or 0.0 0.1 None thermoplastic elastomer more 12-Hydroxystearic acid 75 — 5 16.0 21.4 Heat storage material

1. A heat reservoir, comprising: a plate-shaped porous substrate havingtwo main surfaces; a heat storage material composition impregnating intothe porous substrate; and a coat layer covering at least one of the twomain surfaces of the porous substrate, wherein the heat storage materialcomposition comprises a latent heat storage material and a thermoplasticelastomer and the coat layer is thermostable and radiant heatreflective.
 2. The heat reservoir according to claim 1, wherein thethermoplastic elastomer is at least either an olefin-based thermoplasticelastomer or a styrene-based thermoplastic elastomer.
 3. The heatreservoir according to claim 1, wherein both the two main surfaces ofthe porous substrate are covered by the coat layers and the coat layersare gas-impermeable.
 4. The heat reservoir according to claim 3, whereina surface that connects the two main surfaces of the porous substrate iscovered by the coat layer.
 5. The heat reservoir according to claim 1,wherein the coat layer is a metal layer.
 6. The heat reservoir accordingto claim 2, wherein both the two main surfaces of the porous substrateare covered by the coat layers and the coat layers are gas-impermeable.7. The heat reservoir according to claim 1, wherein a surface thatconnects the two main surfaces of the porous substrate is covered by thecoat layer.
 8. The heat reservoir according to claim 2, wherein asurface that connects the two main surfaces of the porous substrate iscovered by the coat layer.
 9. The heat reservoir according to claim 6,wherein a surface that connects the two main surfaces of the poroussubstrate is covered by the coat layer.
 10. The heat reservoir accordingto claim 2, wherein the coat layer is a metal layer.
 11. The heatreservoir according to claim 3, wherein the coat layer is a metal layer.12. The heat reservoir according to claim 4, wherein the coat layer is ametal layer.
 13. The heat reservoir according to claim 6, wherein thecoat layer is a metal layer.
 14. The heat reservoir according to claim7, wherein the coat layer is a metal layer.
 15. The heat reservoiraccording to claim 8, wherein the coat layer is a metal layer.
 16. Theheat reservoir according to claim 9, wherein the coat layer is a metallayer.